The Louisiana Statewide Lidar Project provided high-resolution elevation data for the entire state—the first to do so with lidar. The dataset is available online through Atlas for public access. Extensive details of the project can be found in the publication, “The Louisiana Statewide Lidar Project“.
Collection date: beginning in 2000 (see metadata packaged with each format)
Resolution: 5 meters
Coordinate reference: NAD83 (GRS80) horizontal and NAVD88 (GEOID99) vertical
Downloadable data format: DEM as .dem, contours as .shp, breaklines as .shp, points as .csv
Metadata included with imagery
There are additional metadata files packaged with each zip file for breaklines, contours, DEM, and points.
Individual lidar panels can be located and downloaded from the Atlas Louisiana lidar map.
To download files in bulk, connect to the Atlas Louisiana lidar FTP site with software like WinSCP.
Atlas Louisiana lidar web services provide a statewide digital elevation model mosaic, including an ArcGIS ImageServer suitable for image analysis.
What is lidar?
When was this lidar data collected?
What is the resolution of the data?
What are the coordinate systems and units of the data?
What areas of the state are covered?
In what file format are the lidar panels stored?
What programs can I use to view the DEM files?
What is the difference between “raw” lidar data and “modified” lidar data?
Where can I find more information on lidar data for Louisiana?
Lidar stands for LIght Detection and Ranging. It uses the same principle as radar except that it uses a laser instead of radio waves. One of the principle uses for lidar is for the measurement of elevation.
The first flights took place in 1999. Check the metadata that is stored within each downloadable zip file for further details.
The horizontal resolution of the DEM is 5 meters. The shapefile contours are 2 feet (vertical). The point data have a vertical accuracy between 6 to 12 inches, and a horizontal accuracy between 3 to 6 feet, with a point spacing of 4 meters (phase 1) and 3 meters (phase 2). The phase of each quad is indicated in its metadata.
The vertical datum is NAVD88 (GEOID99) in feet. The horizontal datum is NAD 83, UTM Zone 15 N (WKID 26915) in meters.
As of April 2009, the LIDAR data on Atlas cover all land areas of the state of Louisiana.
The file format will depend on the form of representation of elevation data. In its raw form, lidar is a series of points stored as x, y, z where x and y can be longitude and latitude; z is the elevation in meters or feet. A simple ASCII file where each line has a coordinate (x,y,z) separated by commas (tabs, spaces, etc.) can be used to represent the data.
Another representation for lidar data is as contour lines. The lines can be stored in a number of different CAD and GIS file formats.
A third representation for lidar data is as a digital elevation model (DEM). This is a raster format with a matrix (grid) with rows and columns. Each cell is of a fixed sized relative to Earth’s surface; each cell holds the average elevation calculated from lidar points for that area of Earth’s surface represented by the cell.
There are additional ways to represent lidar data such as triangular irregular networks (TIN) and profiles.
Currently, Atlas has lidar data in four formats: contours, digital elevation models, edited points, and raw points. The contour data is in shapefile format. The digital elevation models are in the USGS DEM format. The point data – both raw and edited – are in ASCII csv (comma separated value) files.
Also, Atlas has the breakline data that was used in the process to create the contour data. This breakline data is available as a shapefile coverage and is downloadable along with the other data formats.
QGIS, ERDAS Imagine, Esri ArcGIS, and Geomedia are a few of the programs that can read USGS DEM files.
CAD programs such as AutoDesk AutoCAD and Bentley MicroStation can not read DEM files directly, but there are extensions (or companion products) that allow a CAD user to use DEM files with these CAD programs. Examples are Bentley’s Inroads and AutoCAD Civil 3D. Most Civil Engineering applications read USGS DEMs.
The elevation points of the “raw” lidar data include elevations for buildings, highway overpasses, forest canopy, and anything else that prevented the laser beam from reaching “bare earth.” Using post-processing methods, analysts can remove the obstructions and create a set of modified elevations points.
The Louisiana Oil Spill Coordinators Office (LOSCO) along with LSU and 3001, Inc., has created a document titled “The Louisiana Statewide Lidar Project” to provide further information about the lidar available on Atlas. The document includes such information as pre-processing steps, acquisition, post-processing steps, and future procurements.
The QA/QC reports for the fifty-five (55) task areas are available for downloading on Atlas via the lidar downloader. Each lidar panel belongs to one of the 55 task areas. To download all fifty-five (55) reports in one zip file, click here.